In general, carriers are utilized for transporting and storing batches of silicon wafers before during and after processing. The most common current wafer size is 300 mm, although some fabrication facilities are being planned and developed for 450 mm wafers. Typically, wafers are shipped between facilities in shipping containers known as front opening shipping boxes (FOSBs). In such shipping containers, the wafers are loaded into the container horizontally and are seated on shelves. The door is installed which causes the wafers to be raised off of the shelves and be suspended between forward and rearward wafer restraints. The container is then rotated 90 degrees such that the front door is facing upward and the wafers are vertical, spaced between the shelves. The FOSB with wafers is then boxed and shipped to a facility for the processing of the wafers. At the processing facility the wafers may be transferred into another process transport container known as a front opening unified pod (FOUP). The FOUP has a front latching door and receives wafers horizontally to seat on the shelves. Typically the shelves have structure for minimizing contact with the wafers. The wafers are removed from the FOUP for the processing that converts them into integrated circuit chips. Such processing involves multiple steps where the wafers are processed at various processing stations, and between processing steps the wafers are stored and transported within the facility, in the FOUP or other process transport container. The FOUP is typically transported with the wafers by way or overhead conveyors that grasp onto robotic flanges attached to top walls of such containers.
Due to the delicate nature of wafers and their susceptibility to damage by breakage or by contamination by particles or chemicals, it is vital that they be properly protected throughout their transport and processing life in the shipping boxes including FOSBs, process transport containers, including FOUPs. Although there are commonalities between shipping containers such as FOSBs and process transport containers such as FOUPs, they also are inherently different. With regard to shipping between facilities, the FOSB must provide enhanced protection from shock and vibration events within the shipping environment. Thus, great attention is devoted to adequately supporting the peripheries of the wafers and positioning the wafers between, and not contacting, shelves during shipments.
During such processing of semiconductor wafers, the presence of or generation of particulates presents very significant contamination problems. Contamination is accepted as the single largest cause of yield loss in the semi-conductor industry. As the size of integrated circuitry has continued to be reduced, the size of particles which can contaminate an integrated circuit has also become smaller making contamination control all the more. Contaminants in the form of particles may be generated by abrasion such as the rubbing or scraping of the carrier with the wafers, with the carrier covers or enclosures, with storage racks, with other carriers or with processing equipment. Additionally, particulates such as airborne microcontamination can be introduced into the containers through the openings or joints in the covers and enclosures. Additionally, certain gaseous contaminants may create haze on wafers which is also a problem. Thus, a critical function of wafer containers in the processing facility, such as FOUPs, is to protect the wafers therein from such contaminants. Such processing transport containers are typically equipped with gas purging capabilities for maintaining a very clean interior and minimizing any haze growth potential. Fluid conduits to facilitate the introduction and exhaustion of gases such as nitrogen or other purified gasses have been conventionally designed into the bottom walls of the container portions, as opposed to the doors, for example. Substrate containers have additionally been outfitted with various elastomeric grommets in the fluid conduits. These grommets include a bore of sufficient length to contain one or more various operational components inserted therein and positioned between the interior volume of the substrate container and the exterior.